Embodiments of the disclosure relate generally to wind turbines and, more particularly, to mitigating rotor imbalance on wind turbines.
A utility-scale wind turbine typically includes a set of two or three large rotor blades mounted to a hub. The rotor blades and the hub together are referred to as the rotor. The rotor blades aerodynamically interact with the wind and create lift and drag, which is then translated into a driving torque by the rotor. The rotor is attached to and drives a main shaft, which in turn is operatively connected via a drive train to a generator or a set of generators that produce electric power. The main shaft, the drive train, and the generator(s) are all situated within a nacelle, which rests on a yaw system that in some embodiments continuously pivots along a vertical axis to keep the rotor blades facing in the direction of the prevailing wind current to generate maximum driving torque.
In certain circumstances, the wind direction can shift very rapidly, faster than the response of the yaw system, which can result in a yaw error which can generate rotor imbalance (or load imbalance). The rotor imbalance is due to wind shear or yaw misalignment on the operational wind turbines. During such aforementioned transient wind events, the rotor imbalance, which can be sustained for a few seconds or minutes, might damage the wind turbine if operation of the wind turbine continues. Specifically, during such operation of the wind turbine, rotor imbalance can result in unacceptably high loads on the rotor blades, hub, tower, and other components thereof, which can result in damage.
Therefore, there is a need for new and improved control systems and methods for mitigating rotor imbalance on wind turbines.